Liquid peroxide compositions

ABSTRACT

This invention relates to novel peroxide blends which are liquid at 25° C. and lower, their method of preparation and their use in curing peroxide crosslinkable polymers. 
     The blend is a mixture of the meta isomers or the meta and para isomers of the compounds of Formulae I, II and III and optionally Formula IV (all as defined herein) in such proportions that the composition provides a liquid mixture at 25° C. or below which has a high crosslinking efficiency for polymeric materials.

This application is a division of application Ser. No. 08/368,582, filedJan. 4, 1995, which is a divisional of application Ser. No. 08/149,145filed Nov. 5, 1993, now abandoned, which is a continuation ofapplication Ser. No. 07/938,732 filed Aug. 31, 1992, now abandoned.

BACKGROUND OF THE INVENTION FIELD OF THE INVENTION

This invention relates to novel compositions classified in the art ofchemistry as organic peroxides, more specifically to organic peroxideblends which are liquid at room temperature, their method of preparationand their use in curing peroxide crosslinkable polymers.

Still more specifically the organic peroxides comprisealpha-alpha'-ditertiary alkylperoxy derivatives of the meta, or mixedmeta, para isomers of diisopropylbenzene. The compositions are useful incuring peroxide cross-linkable polymers and in initiating polymerizationreactions of suitable monomers.

The novel compositions of the invention include a peroxide blend whichcomprises 5 to 65 parts by weight ofbis(2-t-butylperoxy-2-propyl)benzene, a diperoxide of Formula I ##STR1##from 10 to 55 parts by weight of 1-(2-t-butylperoxy-2-propyl)-3 or4-(2-t-amylperoxy-2-propyl)benzene, a diperoxide of Formula II ##STR2##and from 3 to 55 parts by weight of bis(2-t-amylperoxy-2-propyl)benzene,a diperoxide of Formula III ##STR3##

Wherein the meta to para isomer ratios of each of I, II and III areselected to provide a blend which is liquid at 25° C. or lower.

Preferably, the peroxide blend comprises from about 7 to 61 parts byweight I, from 30 to 55 parts by weight II and from 3 to 47 parts byweight III where the ratio of the meta isomers to the para isomers canvary from at least 1.5:1 to all meta isomers.

More preferably, the peroxide blend comprises from 35 to 60 parts byweight I, from 35 to 55 parts by weight II, from 5 to 20 parts by weightIII and the ratio of the meta isomers to the para isomers can vary fromat least 1.5:1 to all meta isomers.

The peroxide blend may optionally contain small amounts, up to 15% byweight of the peroxide blend, of the meta, para or a mixture of the metaand para isomers of the monoperoxides of Formula IV ##STR4## where R maybe t-butyl or t-amyl and R' may be hydrogen, isopropyl, isopropenyl or2-hydroxy-2-propyl.

The novel blends are efficient crosslinking agents for peroxidecrosslinkable polymers such as low, linear low and high densitypolyethylene, curing agents for ethylene-propylene elastomers such asEPDM, curing agents for polyester resins and initiators for vinylpolymerization.

DESCRIPTION OF THE PRIOR ART

It is well known in the art to use dicumyl peroxide (V),bis(2-t-butylperoxy-2-propyl)benzene (I) andbis(2-t-cumylperoxy-2-propyl)benzene (VI) ##STR5## as crosslinkingagents for polyethylene or ethylene-propylene elastomers (see U.S. Pat.No. Re. 25,941 issued to W. R. Grace & Co., Dec. 14, 1965 and U.S. Pat.No. 4,239,644). The meta and para isomers of I are solid at roomtemperature as are all mixtures thereof. The meta isomer melts about 52°C., the para isomer melts about 79° C. and the eutetic mixture (80% metaisomer) melts about 45° C. Dicumyl peroxide melts about 38° C. (see U.S.Pat. No. 4,202,790). Compound VI is also a solid at room temperature.This leads to serious commercial problems. Blending of solid peroxideswith polymers, such as polyethylene, is commercially avoided due to thedifficulty in obtaining uniform dispersions of the peroxide on thepolymer. A uniform dispersion is essential if one is to obtain auniformly crosslinked polymer in a subsequent step. Therefore the aboveperoxides are melted and kept in the molten state so they can beuniformly metered into the polymer. Careful monitoring of the peroxidetemperature during the melting step and subsequent blending step isrequired to prevent overheating which can result in rapid decompositionand may even result in an explosion. Commercially the melting step hasbeen accomplished by installing melt stations or by using liqua-binswhich are storage bins containing coils with hot water circulatingthrough them. These melting operations have added considerable expenseto the operation. Therefore it is highly desirable to develop acommercial, non-volatile and highly efficient peroxide crosslinkingagent for polymers such as polyethylene, which is a liquid at roomtemperature.

Liquid peroxides such as t-butyl t-cumyl peroxide are too volatile formost commercial crosslinking operations and have been known to causeflash fires. Cumyl isopropylcumyl peroxide (described in U.S. Pat. Nos.2,819,256 and 2,826,570) is a liquid peroxide but is not as efficient asdicumyl peroxide (see U.S. Pat. No. 4,239,644, col. 1 lines 56-57).Consequently, it is not used commercially.

In an attempt to overcome the above shortcomings, liquid peroxide blendshave been prepared where the solid peroxides are dissolved in liquidperoxides in such proportions that a blend is obtained which remainsliquid at room temperature (25° C.) or below. The liquid blend can thenbe readily admixed with polymers such as polyethylene to provide uniformblends of peroxide and polymer prior to the crosslinking operation.

U.S. Pat. No. 4,239,644 issued to Mitsui Petrochemical Industries, Ltd.discloses liquid peroxide blends comprising 70-5 parts by weight dicumylperoxide V and 30-95 parts by weight of a substituted dicumyl peroxideof Formula VII ##STR6## where R" is a 1-3 carbon alkyl group. Preferablythe blend contained 10 to 60 parts dicumyl peroxide and 90 to 40 partsVII. The blends were reported to have efficiency comparable to dicumylperoxide. The patent also describes methods of making these blends byreacting cumene hydroperoxide with a mixture of cumyl alcohol and thesubstituted cumyl alcohol VIII ##STR7## in the presence of an acidcatalyst or by reacting cumyl alcohol with a mixture of cumenehydroperoxide and the substituted cumene hydroperoxide IX ##STR8## inthe presence of an acid catalyst.

U.S. Pat. No. 4,202,790 issued to Hercules Inc. discloses novel blendsof peroxides that are liquid at room temperature. Blend 1 consistsessentially of 25-55% dicumyl peroxide and 75-45% cumyl isopropylcumylperoxide (VII where R" is isopropyl). Blend 2 consists essentially of10-25% bis(2-t-butylperoxy-2-propyl)benzene (I) and 90-75% t-butylisopropylcumyl peroxide (X). ##STR9##

The maximum concentration of I (the preferred crosslinking agent) isonly 25% and the major component X is a rather volatile component.

Blend 1 was prepared by dissolving dicumyl peroxide in cumylisopropylcumyl peroxide. Blend 2 was prepared by dissolvingbis(2-t-butylperoxy-2-propyl)benzene (essentially a 2:1 mixture of themeta and para isomers) in X. The blends were used to cure polyethylenecompositions at 360° F.

U.S. Pat. No. 4,866,137 issued to Ausimont S.p.A. discloses liquidperoxidic compositions containing from 1 to 50 parts by weight of adiperoxide of Formula VI, from 5 to 75 parts by weight of dicumylperoxide of Formula XI ##STR10## where R'" is hydrogen or an alkyl groupcontaining from 1 to 3 carbon atoms and wherein A is selected from themethyl radical or the phenyl radical, optionally substituted.

The meta:para ratio of VI may range from 1.2 to 2.5 and preferably isbetween 1.5 and 2.1. This peroxide is commercially known as Peroxyimon169. This patent states that peroxides of structure VI are moreefficient in the crosslinking of polyethylene. When mixtures of dicumylperoxide and peroxides of Formula VII (Ger. Offen. 2,912,061) are used,approximately 20-35% by weight more peroxide is required than whendicumyl peroxide alone is used. The blends are prepared by reactingcumene hydroperoxide with a mixture of cumyl alcohol and the monoalcoholXII and the diol XIII ##STR11## in the presence of an acid catalyst suchas p-toluenesulfonic acid. In some cases, a peroxide of Formula XI isadded to the peroxide blend after it has been washed and stripped ofvolatiles. The blends were used to crosslink polyethylene.

The Russians have prepared asymmetric diperoxides XV by reactinghydroperoxides with p-diisopropylbenzene hydroxyperoxides of FormulaXIV. ##STR12## R=t-Butyl, t-amyl, t-cumyl R'=t-butyl, t-amyl, t-cumyl

(M. A. Dikii, M. S. Vaida, V. A. Puchin, Izv. Vyssh. Uchebn. Zaved.,Khim. Khim Tekhnol. 1976, 19(6), 873-5(Russ.); C.A. 85, 142748d). To thebest of our knowledge the corresponding meta isomers are not known.

We have unexpectedly found that we can prepare more efficient liquidperoxidic crosslinking compositions by reacting a mixture of t-amyl andt-butyl hydroperoxides with diols of Formula XIII in the presence of anacid catalyst. The diol XIII may be the meta isomer or a mixture of themeta and para isomer.

The reaction product of the diol XIII and the mixture of hydroperoxidesis a mixture of compounds of Formulae I, II, and III. If a mixture ofthe meta and para isomers of the diol XIII is used, then the products I,II, and III will also be mixtures of the meta and para isomers. Thedistribution of the products I, II, and III is dependent upon the ratioof the t-butyl hydroperoxide to the t-amyl hydroperoxide startingmaterials. A slight excess (about 2.1-2.3 moles of hydroperoxide permole of diol) of hydroperoxide is used in all the reactions to insureessentially complete peroxidation of the diol. The ratio of the meta topara isomer of each I, II, and III is approximately the ratio of themeta to para isomers in the starting diol.

If only the meta diol is used or the ratio of meta to para isomer is 4:1or greater and the molar ratio of t-butyl hydroperoxide to t-amylhydroperoxide is 2.35:1 or less, the reaction product after washing andstripping of volatiles is a liquid at 25° C. As the molar ratio of thet-butyl hydroperoxide to t-amyl hydroperoxide decreases, the freezingpoint of the liquid product decreases. The ternary mixture of I, II andIII remains liquid at 15° C. up to a molar ratio of tert-butylgroups/(tert-butyl groups+tert.amyl groups) of 0.59.

If a mixture of the meta and para diols are used, peroxide mixtureswhich are liquid at 25° C. or lower can be obtained if the ratio oft-butyl hydroperoxide to t-amyl hydroperoxide is low enough. A 50--50mixture of the meta and para diol will generate a peroxide liquid at 25°C. if the ratio of t-butyl hydroperoxide to t-amyl hydroperoxide is1.1:1 or less. As the percentage of meta diol in the meta-para diolmixture increases up to 80%, a larger mole ratio of t-butylhydroperoxide to t-amyl hydroperoxide may be used. A 70% meta-30% paramixture of the diol will generate a peroxide liquid at 25° C. if theratio of t-butyl hydroperoxide to t-amyl hydroperoxide is 2.2:1 or less.Optimally to prepare a peroxide mixture liquid at 25° C. and with highcrosslinking efficiency at minimal cost, a diol mixture containing about70% to 90% meta diol and a hydroperoxide mixture containing a mole ratioof t-butyl hydroperoxide to t-amyl hydroperoxide of about 2.25:1 to1.75:1 should be employed.

The meta and para isomers of III are known and are claimed to be usefulas polymer crosslinking agents (U.S. Pat. No. 3,584,059). However, theyare not used commercially because they are not as efficient as thecorresponding t-butyl peroxides (I).

t-Amyl peroxides are not normally employed as commercial crosslinkingagents. t-Amyl peroxides decompose into t-amyloxy radicals which readilybreak down by beta-scission into acetone and ethyl radicals (I. H. Elsonand J. K. Kochi, J. Org. Chem. 39, 2091-2096 (1974)). Ethyl radicals donot abstract hydrogen radicals as readily as methyl radicals or t-butoxyradicals which are generated by the decomposition of t-butyl peroxides(K. Yamamoto and M. Sugimoto, J. Macromol. Sci.-Chem., A13(8),1075(1979)). For abstraction of hydrogen from neopentane andcyclohexane, at 164° C., the ethyl radical is less reactive by a factorof between 6 and 24 (P. Gray, A. A. Herod and A. Jones, Chem. Rev., 71,287 (1971)).

Peroxide crosslinking of polyethylene is initiated by free radicalsgenerated in the peroxide decomposition. The free radicals abstracthydrogen from the polyethylene backbone to generate radical sites on thebackbone. The radical sites on neighboring polymer chains then couple toform a crosslink between polyethylene chains (Encyclopedia of PolymerScience and Engineering, Second Edition, Vol.4, p.385,Wiley-Interscience, New York, N.Y., 1986). Since the ethyl radicalsgenerated from the decomposition of t-amyl peroxides are much lessreactive than the methyl or t-butoxy radicals generated from t-butylperoxides, one would expect the t-amyl peroxides to be much lessefficient polyethylene crosslinking agents than the correspondingt-butyl peroxides. This is verified in comparing the crosslinkingresults of Comparative Examples 1 and 3 in Table II in the Experimentalsection.

Therefore it was quite unexpected that the liquid peroxide blends ofthis invention would be such efficient crosslinking agents. It wasexpected that the liquid peroxide blends containing significant amountsof II and III would have a marked fall off in efficiency when comparedto I. The commercial advantages of liquid peroxides over solid peroxidesin crosslinking applications far outweigh the slight decrease inefficiency experienced when the liquid peroxide blends of this inventionare substituted for I (see Table II in Experimental Section).

SUMMARY OF THE INVENTION

This invention relates to novel peroxide blends which are liquid at roomtemperature (about 25° C.) or at even lower temperatures, their methodof preparation and their use in curing peroxide crosslinkable polymersand to curable compositions containing blends of the peroxide andcurable polymers. The liquid peroxide blends can be uniformly admixedwith polymers such as polyethylene without going through preliminaryexpensive and dangerous melting steps which are necessary at the presenttime with the commercial crosslinking agents which only exist as liquidsat temperatures well above 25° C. They may also be dispersed on solidfillers without employing cryogenic grinding and blending techniqueswhich are required with the solid peroxides.

The blend of peroxides provided by the first composition aspect of thisinvention, comprises a mixture of the meta isomers, or a mixture of themeta and para isomers of Formulae I, II and III, in such proportionsthat the composition is liquid at 25° C. or lower. The peroxide blendcomprises 5 to 65 parts by weight I, 10 to 55 parts by weight II and 3to 55 parts by weight III where the ratio of the meta isomer to the paraisomer is selected to provide a peroxide blend which is liquid at 25° C.or lower. Preferably, the blend comprises from about 7 to 61 parts byweight I, from 30 to 55 parts by weight II and from 3 to 47 parts byweight III and the ratio of the meta isomer to para isomer ranges fromat least 1.5:1 to pure meta isomer. The blend optionally may containsmall amounts of monoperoxides (up to 15% by weight) of Formula IV. Asthe percentage of compounds II and III in the blend decreases, thetendency of the blend to solidify at room temperature (25° C.)increases. As the percentage of the meta isomer increases from 50% to80%, the mixture can tolerate more of the Formula I compound and stillremain liquid at room temperature. Likewise as the percentage of themeta isomer increases at a constant composition of I, II, and III theblend remains liquid at lower temperatures. Since t-amyl hydroperoxideis slightly more expensive than the t-butyl hydroperoxide and compoundIII is slightly less efficient than compound I (see crosslinkingevaluations of comparative Example 1 and comparative Example 3 in TableIII), it is economically advantageous to maximize the amount of compoundI and minimize the amount of compound III in the blend and still providea composition liquid at the desired temperature. The ratio of I:III canbe maximized by optimizing the ratio of the meta and para isomers of I,II, and III in the blend. Preferably, a ratio of about 1.5:1 to about9:1 of the meta isomers to the para isomers or substantially pure metaisomers are employed in the blend. Most preferably a ratio ofapproximately 2.0:1 to 5:1 of the meta isomers to the para isomers oronly the meta isomers are employed in the blend. The freezing point ofthe blend may be further lowered by adding compound III, preferably themeta isomer, to the blend. Both the meta and para isomers of III areliquids but the meta isomer has a lower freezing point.

When the blend is composed of only the meta isomer it comprises 5 to 65parts by weight of a diperoxide of Formula I, from 10 to 55 parts byweight of a diperoxide of Formula II, and from 3 to 55 parts by weightof a diperoxide of Formula III. Preferably it comprises from 30 to 61parts by weight I, from 35 to 47 parts by weight II and from 4 to 16parts by weight III.

When the blend is a mixture of the meta and para isomers of I, II, andIII, it comprises 5 to 65 parts by weight I, from 10 to 55 parts byweight II and from 3 to 55 parts by weight III and the ratio of the metato para isomer is from 1:1 to 99:1. Preferably it comprises from 40 to60 parts by weight I, from 36 to 55 parts by weight II and from 4 to 17parts by weight III and the ratio of the meta to para isomer is from1.5:1 to 9:1. Most preferably the ratio is from 2.0:1 to 5:1.

All the peroxide blends are liquids at 25° C. The lower the mole ratioof t-butyl hydroperoxide to t-amyl hydroperoxide employed in thesynthetic step, the lower the temperature at which the compositions maybe stored without solidifying. Some compositions will remain liquid at15° C. or at even lower temperatures (0°-5° C.). Addition of the metaisomer III also lowers the freezing point.

It is also contemplated by this invention to add some dicumyl peroxide(V) to these blends provided the dicumyl peroxide dissolves in the blendand the blend remains liquid at room temperature (25° C.). Likewiseminor amounts of a peroxide of Formula XI may also be added to the blendas long as the blend remains a liquid at room temperature (25° C.).

The invention also provides in a second composition aspect a curablecomposition comprising a blend of peroxides of the first compositionaspect of this invention admixed with at least one peroxide curablepolymer.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

METHODS OF PREPARATION

The peroxide blends may be prepared by any of the following methods:

1. Mixing the compounds of Formulae I, II, and III in the desiredamounts within the designated ranges.

2. Reacting a mixture of t-butyl hydroperoxide and t-amyl hydroperoxidewith a diol of Formula XIII in a molar ratio of total hydroperoxide todiol of 1.8-3.0:1, preferably 2.0-2.3:1, in the presence of an acidcatalyst. The diol may be the pure meta diol, or a mixture of the metaand para diols containing the desired ratio of meta to para diol.

3. Reacting a mixture of t-butyl hydroperoxide and t-amyl hydroperoxidewith meta diisopropenylbenzene (XVI) or a mixture of meta and paradiisopropenylbenzenes (XVI) in the presence of the dichloride ordibromide of Formula XVII, the monochloride or monobromide of FormulaXVIII or a mixture thereof, where Y is chlorine or bromine ##STR13## 4.Reacting a mixture of t-butyl hydroperoxide and t-amyl hydroperoxidewith meta diisopropylbenzene or a mixture of meta and paradiisopropylbenzenes in the presence of a transition metal salt.

Mixtures of t-butyl hydroperoxide and t-amyl hydroperoxide may beprepared either by mixing the previously prepared hydroperoxides in thedesired ratio, or the two starting materials, t-butyl alcohol and t-amylalcohol, may be mixed in the appropriate ratio and then reacted withhydrogen peroxide in the presence of an acid catalyst, for examplesulfuric acid, to produce a mixture of the two desired hydroperoxidescontaining also di-t-butyl peroxide, di-t-amyl peroxide and t-amylt-butyl peroxide. A hydrocarbon type solvent may be added during thereaction or afterward to provide a solution containing thehydroperoxides at a concentration suitable for further reaction toprepare the liquid mixtures containing the peroxides of Formulae I, IIand III.

Another alternative method for the direct preparation of thehydroperoxide mixture is to absorb isobutylene and isopentenesimultaneously in aqueous sulfuric acid and then treat the mixture ofsulfate esters so formed with hydrogen peroxide. The mixture may also beprepared by separately absorbing each of the two olefinic hydrocarbonsin sulfuric acid, mixing the esters and then treating with hydrogenperoxide.

METHOD 1

This method is not a very commercially feasible route to the liquidperoxide blends because it requires the individual preparation of eachof the components prior to preparing the blend. Compound I can beprepared by reacting t-butyl hydroperoxide with a diol of Formula XIIIusing a molar ratio of t-butyl hydroperoxide to diol of approximately2.0-2.3 to 1 in the presence of an acid catalyst (U.S. Pat. No.3,584,059). Compound I is available commercially from Hercules Inc.under the trade name "Vulcup", from Elf Atochem Italia under the tradename "Peroxyimon F" and from Elf Atochem N.A. under the trade name"Luperox 802". Compound III can be prepared by reacting t-amylhydroperoxide with a diol of Formula XIII using a molar ratio ofhydroperoxide to diol of 2.0-2.5:1 in the presence of an acid catalyst.Compound II can be prepared by reacting t-butyl hydroperoxide with adiol of Formula XIII using a molar ratio of t-butyl hydroperoxide todiol of approximately 0.9-1.1:1 in the presence of an acid catalyst. Thehalf product of Formula IV, where R is t-butyl and R' is2-hydroxy-2-propyl, is obtained. The half product is then reacted witht-amyl hydroperoxide using a mole ratio of t-amyl hydroperoxide to halfproduct of approximately 0.9-1.4 to 1 in the presence of an acidcatalyst. Compound II may also be prepared by reacting the diol witht-amyl hydroperoxide first then reacting the resulting half product(where R is t-amyl) with t-butyl hydroperoxide (see C.A. 85, 142748d).

METHOD 2

This is the preferred method of preparing the liquid peroxide blends.The reaction of t-butyl hydroperoxide withbis-(2-hydroxy-2-propyl)benzene in the presence of acid condensationcatalysts is well known in the art (see Can. Pat. 754,613). Method 2 isa modification of this procedure where a mixture of t-butylhydroperoxide and t-amyl hydroperoxide is used instead of t-butylhydroperoxide alone.

The peroxide blends may be prepared by reacting a mixture of t-butylhydroperoxide and t-amyl hydroperoxide with a diol of Formula XIII in amolar ratio of total hydroperoxide to diol of 1.8-3.0 to 1. The diol maybe the pure meta diol, or a mixture of the meta and para diols where themixture contains the desired percentage of the meta diol. Suitable acidcatalysts are any strong organic or inorganic acid catalyst such asperchloric acid, sulfuric acid, phosphoric acid, hydrochloric acid,benzenesulfonic acid, methanesulfonic acid, p-toluenesulfonic acid,--SO₃ H substituted ion exchange resins, trifluoroacetic acid and acidshaving pKa≦2.5 in aqueous solution at 25° C. Other acidic catalystssuitable for the reaction include anhydrides of carboxylic acids havinga pKa>2.85 as per U.S. Pat. No. 4,198,528 and synthetic SiO₂ --Al₂ O₃(Japan Tokkyo Koko 81 20,568; C.A. 95, 42650). When using an aqueousstrong acid solution such as 60-80% sulfuric acid, the reaction isgenerally carried out at temperatures above -5° C. and below 40° C. Theoptimum reaction temperature is dependent upon the identity and amountof the acid condensation catalyst and the amount of water present. Thereaction may be run without a solvent or in the presence of an inertsolvent or mixture of solvents, for example, aromatic hydrocarbons suchas benzene, toluene, cumene, xylene, and the like, aliphatichydrocarbons such as pentane, hexane and heptane, cycloaliphatichydrocarbons such as cyclohexane, ethers such as diethyl ether andmethyl t-butyl ether and chlorinated hydrocarbons such as methlyenechloride, chloroform, chlorobenzene, and dichlorobenzene.

Preferably, a slight stoichiometric excess of a mixture of t-butyl andt-amyl hydroperoxide is reacted with meta bis(2-hydroxy-2-propyl)benzeneXIII (or a mixture of the meta and para isomers of XIII) in the presenceof aqueous sulfuric acid. Preferably the diol XIII is slurried in themixture of hydroperoxides at 15°-30° C. using a mole ratio ofhydroperoxide to diol of approximately 1.8-2.5 to 1. Reaction isinitiated by adding the acid, preferably 68% to 73% aqueous sulfuricacid, to the mixture while controlling the reaction temperature between15°-30° C. and most preferably at 20° C.±2° C. Preferably the mole ratioof sulfuric acid to diol is 1.8-3.5 to 1 and most preferably the moleratio is 2.0-3.0 to 1. The reaction can readily be monitored by gaschromatography. The ratio of the products can be varied by varying themole ratio of the t-butyl hydroperoxide to the t-amyl hydroperoxide from0.25-2.5 to 1. Preferably the mole ratio of the t-butyl hydroperoxide tot-amyl hydroperoxide is 1.0-2.35 to 1.0. Most preferably the ratio is1.5-2.25 to 1.0. Preferably the mole ratio of hydroperoxide to diol is2.0-2.5 to 1. Most preferably the ratio is 2.0-2.3 to 1.

The peroxide blend may also be prepared by adding a portion of thehydroperoxides to the diol, adding a corresponding portion of the acidcatalyst and allowing reaction to occur, adding another portion of thehydroperoxide mixture and then a corresponding portion of the acid untilthe additions are complete and then stirring until reaction isessentially complete. Likewise, the diol may be slurried in one of thehydroperoxides, a corresponding amount of acid added and reactionallowed to occur. Then the other hydroperoxide may be added and the restof the acid added and the resulting mixture stirred until reaction isessentially complete. If this method is employed, it is preferable toreact the t-amyl hydroperoxide first. The order of addition may bereversed where the aqueous sulfuric acid is added to the diol at 0°-5°C. and then the hydroperoxides are added, either as a mixture orincrementally, to the acid slurry at 0°-10° C. The reaction temperatureis then allowed to rise slowly up to as high as 40° C., preferably onlyas high as 30° C. and the reaction mixture is stirred until essentiallyall of the diol has reacted.

After reaction is complete, the crude product is separated from the acidcatalyst or the acid is neutralized. Preferably, the acid layer isseparated and the crude product is washed with an alkali metal hydroxidesolution, preferably 5-15% aqueous sodium hydroxide or potassiumhydroxide, washed with water until neutral and stripped of volatiles.Addition of an inert solvent such as those previously mentioned canspeed up the separations and minimize mechanical loss of product.

METHOD 3

Comprises the reaction of a t-butyl/t-amyl hydroperoxide mixture with1,3-bis(2-chloro-2-propyl)benzene,1-(2-chloro-2-propyl)-3-isopropenylbenzene, a mixture of 1,3 and1,4-bis(2-chloro-2-propyl)benzene, a mixture of1-(2-chloro-2-propyl)-3-isopropenylbenzene and1-(2-chloro-2-propyl)-4-isopropenylbenzene or a mixture thereof, in thepresence of meta diisopropenylbenzene or a mixture of meta and paradiisopropenylbenzene, under relatively non-aqueous conditions. Thereaction generates peroxides I, II, and III and liberates hydrogenchloride. The reaction may be catalyzed by the addition of an unhinderedphenol. Under these conditions the hydrogen chloride generated reactswith the diisopropenylbenzenes to regenerate thebis(2-chloro-2-propyl)benzene, 1-(2-chloro-2-propyl)-3- or4-isopropenylbenzene or mixture thereof. The 1-(2-chloro-2-propyl)-3- or4-isopropenylbenzene can react with more hydrogen chloride later in thereaction to form 1,3- or 1,4-bis(2-chloro-2-propyl)benzene or can reactwith a hydroperoxide to form 1-(2-t-alkylperoxy-2-propyl)-3- or4-(2-chloro-2-propyl)benzene which can then react with morehydroperoxide to form compound I, II or III.

The bis(2-chloro-2-propyl)benzene/(2-chloro-2-propyl)isopropenylbenzenesolution can be generated in situ by adding dry hydrogen chloride todiisopropenylbenzene until about 5-20% of the isopropenyl groups areconverted to 2-chloro-2-propyl groups. Alternativelybis(2-chloro-2-propyl)benzene can be prepared by adding dry hydrogenchloride to diisopropenylbenzene until essentially all the isopropenylgroups are converted to 2-chloro-2-propyl groups. Thebis(2-chloro-2-propyl)benzene may alternatively be diluted to thedesired concentration with diisopropenylbenzene or it can be addeddirectly to the mixture of diisopropenylbenzene, t-butyl hydroperoxide,t-amyl hydroperoxide and phenol.

Preferably about 5-20%, most preferably 7-12%, of the isopropenyl groupsof the diisopropenylbenzene are converted to 2-chloro-2-propyl groups,the mixture of hydroperoxides is added to it and a phenol catalyst isadded. Increasing the concentration of the 2-chloro-2-propyl groupsincreases the reaction rate but usually increases the amount ofimpurities generated as well. The mole ratio of isopropenyl groups plus2-chloro-2-propyl groups to hydroperoxide groups can vary from 0.5-1.3to 1.

The reactants may be charged to the reactor in any order but it ispreferable to add either the phenol or the(2-chloro-2-propyl)benzene/1-(2-chloro-2-propyl)isopropenylbenzenesolution last. Preferably, a solution of the phenol in the hydroperoxidemixture is added to the solution of the 2-chloro-2-propylbenzenes indiisopropenylbenzene.

The system does not have to be completely anhydrous but water does havea rate retarding effect. It has been found beneficial in some cases,from an ease of handling standpoint, to use liquified phenol whichcontains about 9% water. When using liquified phenol, the amount ofphenol used must be increased by about 10% to override the rateretarding effect of the water. Other suitable unhindered phenols includeortho, meta and para cresols, chlorophenols, bromophenols,methoxyphenols, ethylphenols, isopropylphenols and para-t-butylphenol.From a practical standpoint, it is advantageous to use an inexpensive,low molecular weight phenol which can be readily extracted out of thereaction mixture with aqueous caustic. Phenol and the meta and paracresols or mixtures thereof are especially suitable.

The ratio of the products I, II and III can be varied by varying themole ratio of the t-butyl hydroperoxide to the t-amyl hydroperoxide from0.25-2.5 to 1. Preferably the mole ratio of t-butyl hydroperoxide tot-amyl hydroperoxide is 1.0-2.35 to 1 and most preferably the ratio is1.5-2.25 to 1. The ratio of the meta isomers to the para isomers of I,II and III may be varied by varying the ratio of the starting meta andpara diisopropenylbenzenes. The ratio of the meta diisopropenylbenzeneto the para diisopropenylbenzene should be at least 1:1 and morepreferably should be at least 2:1 and most preferably the ratio shouldbe at least 2.5:1 or the diisopropenylbenzene should be exclusively themeta isomer.

The reaction is run in the temperature range of 10°-50° C., preferably15°-45° C. Since the phenol acts as a catalyst, the reaction temperatureand time are dependent upon the amount of phenol added. When smallamounts of phenol are added, the reaction will take longer and should berun at a higher temperature than when larger amounts of phenol areadded. In practice, it is preferable to start the reaction out at a lowtemperature, 15°-25° C., while the bulk of the reaction is taking placeand then program the temperature up as the reaction slows down. Thereaction can be monitored by gas chromatography so one of skill in theart may easily determine if the temperature should be raised or lowered.

After the reaction is essentially complete, the crude reaction mixtureis washed with dilute solutions of sodium or potassium hydroxide toremove the phenol and residual hydroperoxides and to hydrolyze anyresidual (2-chloro-2-propyl)benzenes. The crude product is then washedwith water to neutral and the volatiles are stripped off under reducedpressure.

The peroxide blend may also be prepared by reactingmeta-diisopropenylbenzene or a mixture of meta- andpara-diisopropenylbenzene with a mixture of t-butyl and t-amylhydroperoxides in the presence of aqueous hydrochloric acid using theprocedure of Example 2 in U.S. Pat. No. 4,864,064.

METHOD 4

This method involves the metal catalyzed decomposition of hydroperoxidesin the presence of isopropylbenzenes. M. S. Kharasch and A. Fono (J.Org. Chem. 23. p.324(1958)) reported on the preparation of alpha-cumylt-butyl peroxide by the reaction of t-butyl hydroperoxide with cumene inthe presence of a metal salt. In the same mannerbis(2-t-butylperoxy-2-propyl)benzene (I) may be prepared by the metalcatalyzed decomposition of t-butyl hydroperoxide in the presence ofdiisopropylbenzene. A mole ratio of 4:1 t-butyl hydroperoxide todiisopropylbenzene is required. If a mixture of t-butyl hydroperoxideand t-amyl hydroperoxide is used and the molar ratio of hydroperoxide todiisopropylbenzene is at least 4:1 then one obtains a product containingperoxides I, II and III.

The reaction can be catalyzed by salts of vanadium, chromium, manganese,iron, cobalt, nickel and copper. The salts may be inorganic such as thehalides and sulfates or organic such as the naphthenates,acetylacetonates and carboxylates of organic acids. Since thehydroperoxides act both as oxidizing and reducing agents toward metalsalts, the salts used may have the metal in any of its oxidation states.Preferably one may use cuprous chloride, cupric chloride, cobaltousacetate, cupric 2-ethylhexanoate, cobaltous 2-ethylhexanoate or cobalticstearate.

The reaction time may vary from a few hours to a few days depending uponthe catalyst type and amount, reaction temperature, the presence orabsence of a solvent and the amount of hydroperoxide employed.Preferably the hydroperoxides are added in portions and the reaction isrun between 50° and 80° C. The higher the catalyst concentration, thelower the reaction temperature should be held to eliminate or minimizeinduced decomposition of the hydroperoxides. Suitable inert solventsinclude benzene, toluene, methanol, isopropanol, ethanol, t-butanol,hexane, chloroform and acetic acid. Aqueous solutions of the metal saltmay also be employed.

The catalyst concentration may vary from about 0.001 to about 0.1 moleof catalyst per mole of hydroperoxide. Preferably about 0.01 to 0.05mole of catalyst per mole of hydroperoxide is employed.

Preferably, after the reaction is essentially complete, any catalystresidues are filtered off, the crude reaction product is treated with5-10% additional hydroperoxide 60-80% aqueous sulfuric acid at 20°-30°C. for 10-30 minutes to convert any 2-hydroxy-2-propylbenzene sideproducts to either I, II or III. The acid is separated, the crudeproduct washed with 5-10% sodium or potassium hydroxide, washed withwater to neutral and the volatiles stripped off under reduced pressure.

The hydroperoxides may be added sequentially or as mixtures. The ratioof the products I, II and III may be varied by varying the mole ratio ofthe t-butyl hydroperoxide to the t-amyl hydroperoxide from 0.25-2.5to 1. Preferably, the mole ratio of the t-butyl hydroperoxide to thet-amyl hydroperoxide is 1.0-2.35 to 1 and most preferably the ratio is1.5-2.25 to 1. The ratio of the meta isomers to the para isomers ofcompounds I, II and III may be varied by varying the meta to para ratioof the starting diisopropylbenzenes. The ratio of the meta isomers tothe para isomers should be at least 1:1 and preferably should be atleast 1.5:1, or exclusively the meta isomer.

The blends prepared by Methods 2, 3 and 4 may be modified to obtain alower freezing point by adding additional compound III, preferably themeta isomer, prepared as described in Method 1.

UTILITY

The novel blends of this invention are useful in the crosslinking ofnatural or synthetic materials which are thermoplastic or elastomeric innature and which can be crosslinked through the action of a free radicalcrosslinking agent. Being liquids, the novel blends of this inventioncan be uniformly dispersed into the polymeric materials without goingthrough expensive and potentially hazardous melting steps. Examples ofsuitable crosslinkable polymeric materials include low densitypolyethylene, linear low density polyethylene, high densitypolyethylene, ethylene-propylene copolymers and terpolymers,ethylene-vinyl acetate copolymers, chlorinated polyethylene, siliconerubber, natural rubber(cis-1,4-polyisoprene), polyurethane rubber,1,4-polybutadiene, styrene-butadiene rubber, acrylonitrile-butadienerubber, isoprene rubber, acrylonitrile-butadiene-styrene copolymers,styrene-butadiene-styrene rubber, styrene-isoprene-styrene copolymersand chloroprene rubber. Reference to the crosslinkable polymers can befound in Rubber World, "Elastomer Crosslinking with Diperoxyketals",October, 1983, pp. 26-32 and Rubber and Plastics News, "OrganicPeroxides for Rubber Crosslinking", Sep. 29, 1980, pp. 46-50.

The amount of the peroxide blend crosslinking agent present in thecrosslinkable polymeric composition should be sufficient to afford thedesired degree of crosslinking. The amount of peroxide blend can rangefrom 0.1 to 10 parts by weight for each 100 parts by weight of polymericcompound. Preferably, 0.5 to 5 PHR (parts per hundred parts resin) ofthe peroxide blend will be employed.

The crosslinkable composition containing the proper amount of theperoxide blend is heat cured for a time sufficient to obtain the desireddegree of crosslinking. The heat curing has a temperature-timerelationship which is dependent on the crosslinkable polymer and theamount and composition of the peroxide blend. The crosslinking ispreferably carried out at 300°-500° F. (149°-260° C.) in 0.5 to 30minutes.

The polymeric compositions may also contain one or more fillers orcarriers. Some of the commonly used fillers are calcium carbonate,calcium silicate, silica, various grades of clay, carbon black, titaniumdioxide and alkaline earth metal carbonates. The polymeric compositionsto be crosslinked may also contain co-agents such as triallyl cyanurate,triallyl isocyanurate, liquid 1,2-polybutadiene and various polyfunctional methacrylates and acrylates.

The novel blends of this invention are also useful as polymerizationinitiators for vinyl monomers such as styrene, butadiene, isoprene,acrylonitrile, vinyl chloride, ethyl acrylate, methyl methacrylate,vinyl acetate, acrylic acid, vinyl stearate, vinylidene chloride andmixtures thereof. The novel blends of this invention are also useful asinitiators for grafting vinyl monomers onto ethylene and propylene homo-or copolymers. Examples of suitable grafting monomers include maleicanhydride, maleimide and N-substituted maleimides, acrylic andmethacrylic acids, mono and diesters of maleic acid, styrene,acrylonitrile and acrylamide. The novel blends are also useful forcuring polyester resins.

EXPERIMENTAL

The following examples are presented to provide a more detailedexplanation of the present invention and of the preferred embodimentsthereof and are intended as illustrations and not limitations.

The meta isomer of bis(2-hydroxy-2-propyl)benzene was obtained fromSumitomo Chemical Co. The para isomer was obtained from Mitsui ChemicalCo. Mixtures of the meta and para isomers were prepared by mixing thetwo isomers in the indicated amounts. The meta and para diols and theirmixtures were also prepared by alkylating benzene with propylene in thepresence of AlCl₃, separating the diisopropylbenzene fraction, oxidizingit with air using conventional techniques, extracting the meta and paradihydroperoxides of diisopropylbenzene with aqueous caustic and reducingthe aqueous extract with sodium hydrogen sulfide in conventional fashionto form an aqueous suspension of the dialcohol containing about 35% paraisomer and about 65% of the meta isomer. Aqueous t-butyl hydroperoxide(70%) is a product of Arco Chemical Co.

t-Amyl Hydroperoxide (82%-85%) is a product of Elf Atochem NorthAmerica, Inc.

Dutra® CO 054 is an ethylene/propylene copolymer.

Riblene® CF 2203 is a low density polyethylene.

Anox® HB is a 2,2,4-trimethyl-1,2-dihydroquinoline polymer.

Sclair® is a high density polyethylene resin.

The reactions of Examples I through XXXIII and Comparative Examples 1through 5 were carried out in stirred jacketed reactors equipped with athermometer and a bottom outlet valve.

The curing reactions of Examples XXXIV through XXXVI were conducted in aMonsanto ODR-100 oscillating disk rheometer (Model R-100). Scorch timeswere determined in Examples XXXV and XXXVI using a Mooney viscometer.

Monoperoxides present as by-products in any of the bisperoxides preparedas indicated may be removed by the method of U.S. Pat. No. 3,584,059,the disclosure of which is incorporated herein by reference.

Gas and liquid chromatographic analyses are reported as weight percent.

EXAMPLE I

To the reactor were added 138 grams of a heptane solution containing0.26 mole of t-butyl hydroperoxide and 0.26 mole of t-amylhydroperoxide, 6.1 grams of water and 56 grams of dialcohol of FormulaXIII containing about 0.167 mole of the meta isomer and 0.089 mole ofthe para isomer. The stirrer was activated and the slurry cooled to 5°C. by pumping cold water through the jacket. To the cooled slurry wasadded 119 grams (0.85 mole) of 70% sulfuric acid over 1 hour undernitrogen while controlling the temperature between 5°-8° C. bycirculating ice water through the reactor jacket. After the addition wascomplete, the reaction was stirred an additional hour at 5°-8° C.

The crude reaction mixture was settled and the lower acid layerseparated. The organic layer was then washed twice at 60° C. with 500 mlportions of 10% aqueous soda and twice with 250 ml portions of deionizedwater. The heptane was removed by steam distillation and the residuedried at 65° C. under vacuum. The product was a liquid, weighed 67 gramsand had an Act(O) content of 7.43%. Gas chromatographic analysisindicated the product was a mixture consisting of 19% meta I, 12% paraI, 26% meta II, 20% para II, 8% meta III and 7% para III. The productremained a liquid at 15° C.

EXAMPLE II

The procedure of Example I was repeated except the dialcohol of FormulaXIII was exclusively the meta isomer. The dried product was a liquid,weighed 60 grams and had an Act (O) content of 7.8%. Gas chromatographicanalysis indicated the product was a mixture consisting of 30% meta I,43% meta II and 16% meta III. The product remained a liquid at 15° C.

EXAMPLE III

The procedure of Example I was repeated except the heptane solutioncontained 0.13 mole of t-butyl hydroperoxide and 0.39 mole of t-amylhydroperoxide. The dialcohol of Formula XIII was a mixture of 0.167 moleof the meta isomer and 0.089 mole of the para isomer. The dried productwas a liquid, weighed 66 grams and had an Act(O) content of 7.27%. Gaschromatographic analysis indicated the product was a mixture consistingof 6% meta I, 3% para I, 22% meta II, 15% para II, 24% meta III and 19%para III. The product remained a liquid at 15° C.

EXAMPLE IV

The procedure of Example I was repeated except the heptane solutioncontained 0.124 mole of t-butyl hydroperoxide and 0.373 mole of t-amylhydroperoxide. The meta isomer (0.234 mole) of the dialcohol of FormulaXIII was used. The dried product was a liquid, weighed 56 grams and hadan Act(O) content of 7.62%. Gas chromatographic analysis indicated theproduct was a mixture consisting of 9% meta I, 37% meta II and 43% metaIII. The product remained a liquid at 15° C.

EXAMPLE V

To the reactor were added 84.2 grams (1.0 mole) of 88% aqueous t-butylalcohol, 100 grams (1.0 mole) of 88% aqueous t-amyl alcohol and 197grams of heptane. The stirrer was activated and 126 grams (2.6 mole) of70% hydrogen peroxide and 126 grams (0.9 mole) of 70% sulfuric acid wereadded simultaneously over a period of 1 hour while maintaining thetemperature at 35° C. After addition was complete, the resulting mixturewas stirred for an additional two hours at 35° C. At the end of the stirperiod, the aqueous layer was settled and separated. Gas chromatographicanalysis of the heptane solution (386 grams) indicated the presence of20.7% t-butyl hydroperoxide and 23.9% t-amyl hydroperoxide.

The procedure of Example I was repeated except 113 grams of the aboveheptane solution (containing 0.26 mole of t-butyl hydroperoxide and 0.26mole of t-amyl hydroperoxide) was used as the hydroperoxide solution.The dialcohol of Formula XIII was a mixture of 0.167 mole of the metaisomer and 0.089 mole of the para isomer. The dried product was aliquid, weighed 66 grams and had an Act(O) content of 7.53%. Gaschromatographic analysis indicated the product was a mixture consistingof 15% meta I, 11% para I, 25% meta II, 21% para II, 9% meta III and 8%para III. The product remained a liquid at 15° C.

EXAMPLE VI

Following a procedure analogous to that described in Example V, 21 gramsof 88% t-butyl alcohol, 75 grams of 88% t-amyl alcohol and 100 grams ofn-heptane were stirred with 63 grams of 70% hydrogen peroxide in thepresence of 70% sulfuric acid to provide 199 grams of a heptane solutionof hydroperoxides. Gas chromatographic analysis of the heptane solutionindicated it contained 10% t-butyl hydroperoxide and 30% t-amylhydroperoxide.

130 grams of the heptane solution from above (contains 0.144 mole oft-butyl hydroperoxide and 0.375 mole t-amyl hydroperoxide) were stirredwith 126 grams of 70% sulfuric acid, 6.1 grams of water and 0.167 moleof the meta isomer and 0.089 mole of the para isomer of the dialcohol ofFormula XIII. The product, after workup and drying, was a liquid,weighed 67 grams and had an Act(O) content of 7.27%. Gas chromatographicanalysis indicated the product was a mixture consisting of 5% meta I, 3%para I, 21% meta II, 17% para II, 23% meta III and 19% III. The productremained a liquid at 15° C.

EXAMPLE VII

To the reactor was added 20.4 grams (0.105 mole) of1,3-bis(2-hydroxy-2-propyl)benzene, 19.8 grams (0.154 mole) of aqueous70% t-butyl hydroperoxide, 9.8 grams (0.077 mole) of aqueous 82% t-amylhydroperoxide and 1.5 grams of water. The stirrer was activated and themixture stirred vigorously to form a thick slurry. The temperature ofthe slurry was adjusted to 14° C. by pumping cold water through thejacket. To the cooled slurry was added 44.1 grams (0.316 mole) of 70%sulfuric acid dropwise over 13 minutes while controlling the temperaturebetween 14°-21° C. by circulating 15°-18° C. water through the reactorjacket. After the addition was complete, the reaction was stirred anadditional hour at 20°-21° C.

The crude reaction mixture was diluted with 40 mls of hexane and 50 mlsof water and the lower acid layer settled and separated. The organiclayer was then washed with 50 ml portions of 71/2% sodium hydroxidesolution, water and saturated sodium bicarbonate solution. All of thewashes were of 5 minute duration at 3° C. The washed hexane solution wasdried over 10 grams of anhydrous sodium sulfate, filtered and the hexanewas stripped off on a rotary evaporator under water aspirator vacuum.The residue was stripped an additional 45 minutes at 50°-60° C. with avacuum pump to remove any residual volatiles. The residue was a paleyellow liquid weighing 32.5 grams. Liquid chromatographic analysis ofthe product indicated it was a mixture consisting of 49.1% meta I, 36.2%meta II and 7.3% meta III. It did not solidify upon storage at roomtemperature.

EXAMPLE VIII

To the reactor was added 20.4 grams (0.105 mole) of1,3-bis(2-hydroxy-2-propyl)benzene, 14.9 grams (0.116 mole) of aqueous70% t-butyl hydroperoxide, 14.5 grams (0.116 mole) of aqueous 83% t-amylhydroperoxide and 2.0 grams of water. The stirrer was activated and 26.8grams (0.21 mole) of 77% sulfuric acid were added dropwise over 20minutes while controlling the reaction temperature at 17°-22° C. Thereaction was stirred an additional 2 hours at 20° C. and then worked upas in Example I. The stripped residue was a light yellow liquid thatweighed 29.8 grams. The gas chromatographic analysis indicated theresidue was a mixture consisting of 36.1% meta I, 43.5% meta II and13.4% meta III. The residue was placed in a refrigerator overnight at0°-5° C. and did not solidify.

EXAMPLE IX

To the reactor was added 16.3 grams (0.084 mole) of1,3-bis(2-hydroxy-2-propyl)benzene, 4.1 grams (0.021 mole) of1,4-bis(2-hydroxy-2-hydroxy-2-propyl)benzene, 19.8 grams (0.154 mole) ofaqueous t-butyl hydroperoxide, 9.6 grams (0.077 mole) of aqueous t-amylhydroperoxide and 1.5 grams of water. The stirrer was activated and 26.8grams (0.21 mole) of 77% sulfuric acid were added dropwise over 12minutes while controlling the temperature at 23°-31° C. The reaction wasstirred an additional 11/2 hours at 30° C. and then worked up as inExample I. The residue was a light yellow liquid that weighed 29.2grams. The product remained liquid upon storage at room temperature (23°C.). Liquid chromatographic analysis indicated the product containedapproximately 40.1% meta I, 13.6% para I, 28.2% meta II, 10.8% para II,4.9% meta III and 2.4% para III. A sample of the product was stored inthe refrigerator at 0°-5° C. The sample remained liquid for 3 days.

EXAMPLES X-XXX

Examples X to XXX were carried out using the general procedure ofExample VII. The total amount of bis(2-hydroxy-2-propyl)benzene used was20.4 grams (0.105 mole). The percent meta isomer and percent para isomerin the starting diol is given in Table I. The mole ratio ofhydroperoxide to diol was 2.2 to 1. The mole ratio of t-butylhydroperoxide to t-amyl hydroperoxide used in each example is also givenin Table I. 70% aqueous t-butyl hydroperoxide was used as such, 85%aqueous t-amyl hydroperoxide was diluted with water to 78% before using(Examples XXIII and XVIV used 70% instead of 78% t-amyl hydroperoxide).The acid catalyst used was 44.1 grams (0.316 mole) of 70% sulfuric acid.The acid was added over approximately 15 minutes while holding thereaction temperature at 14°-16° C. by circulating cold water through thereactor jacket. After the addition was complete the reaction was stirredan additional hour at 20°-22° C.

The crude product was worked up and stripped according to the procedurein Example VII. All the products were pale yellow liquids that remainedliquid at 23° C. Table I demonstrates that many of the products remainedliquid upon storage at 15° C. and some remained liquid upon storage at3° C. The approximate product compositions are also found in Table I.

Comparative Example 1

1,3-Bis(2-t-butylperoxy-2-propyl)benzene (meta I) was prepared byreacting 29.7 grams (0.231 mole) of aqueous 70% t-butyl hydroperoxidewith 20.4 grams (0.105 mole) of 1,3-bis(2-hydroxy-2-propyl)benzene inthe presence of 26.8 grams (0.21 mole) of 77% sulfuric acid according tothe procedure of Example I. The stripped product weighed 32.6 grams. Itcrystallized upon cooling and had a melting point of 45°-52° C. Thisexample is for comparative purposes and does not fall under thespecifications of this invention. The peroxide assay was 97% oftheoretical.

Comparative Example 2

1,3-Bis(2-t-amylperoxy-2-propyl)benzene (meta III) was prepared byreacting 28.1 grams (0.231 mole) of aqueous 85.7% t-amyl hydroperoxidediluted with 3.2 grams of water with 20.4 grams (0.105 mole) of1,3-bis(2-hydroxy-2-propyl)benzene in the presence of 44.1 grams (0.316mole) of 70% sulfuric acid according to the procedure of Example VII.The stripped product was a yellow liquid which did not solidify in afreezer at -17° C. The product weighed 29.9 grams and assayed 95% as1,3-bis(2-t-amylperoxy-2-propyl)benzene and contained about 5%1-(2-t-amylperoxy-2-propyl)-3-(2-hydroxy-2-propyl)-benzene. The productremained a liquid at 15° C.

Comparative Example 3

1,4-Bis(2-t-amylperoxy-2-propyl)benzene (para III) was prepared byreacting 28.1 grams (0.231 mole) of aqueous 85.7% t-amyl hydroperoxidediluted with 3.2 grams of water with 20.4 grams (0.105 mole) of1,4-bis(2-hydroxy-2-propyl)benzene in the presence of 44.1 grams (0.316mole) of 70% sulfuric acid according to the procedure of Example VII.The stripped product was a yellow liquid which remained liquid at 15° C.The product weighed 32.0 grams.

Comparative Example 4

Comparative Example 3 was repeated except the dialcohol of Formula XIIIwas a mixture of 12.2 grams (0.063 mole) of the meta isomer and 8.2grams (0.042 mole) of the para isomer. The stripped product was a yellowliquid and did not solidify in the freezer at -17° C. The productcontained 55.4% 1,3-bis(2-t-amylperoxy-2-propyl)benzene (meta III) and41.9% of the para isomer (para III).

Comparative Example 5

A heptane solution (647 grams) containing 1.84 moles of t-amylhydroperoxide and 174 grams of an aqueous suspension composed of 17.5grams of water, 0.53 mole of the meta isomer of the dialcobol of FormulaXIII and 0.28 mole of the para isomer were added to the reactor. Thestirrer was activated and the slurry cooled to 5° C. by pumping coldwater through the jacket. To the cooled slurry, under a nitrogenatmosphere, 331 grams of 70% aqueous sulfuric acid solution was slowlyadded over 30 minutes while maintaining the temperature at 5°-8° C.After the addition was complete, the reaction was stirred an additionalhour at 5°-8° C.

The crude reaction mixture was settled and the lower acid layerseparated. The organic layer was then washed twice at 60° C. with 500 mlportions of 10% aqueous soda and twice with 200 ml portions of deionizedwater. The heptane was removed by steam distillation and the residuedried at 65° C. under vacuum. The product was a liquid and had an Act(O)content of 6.97%. Gas chromatographic analysis indicated the product wasa mixture consisting of 45% meta III and 36% para III.

EXAMPLES XXXIa-XXXIIIa

Examples XXXI-XXXIII were carried out using the general procedure usedfor Examples X-XXX. Examples XXXIa and XXXIIa were prepared by diluting9 parts of the products of Examples XXXI and XXXII with 1 part1,3-bis(2-t-amylperoxy-2-propyl)benzene from Comparative Example 2.Example XXXIIIa was prepared by diluting 9 parts of the product ofExample XXXIII with 2 parts 1,3-bis(2-t-amylperoxy-2-propyl)benzene. Theproducts of Examples XXXIa, XXXIIa and XXXIIIa remained liquids at lowertemperatures than the products of XXXI, XXXII and XXXIII. Theapproximate compositions of the diluted and undiluted samples are foundin Table II.

EXAMPLE XXXIV

Crosslinking Evaluations in High Density Polyethylene

The products from Examples VII and VIII and Comparative Examples 1 and 2were evaluated in the crosslinking of high density polyethylene. Allsamples were run on an equal active oxygen basis, therefore samples lessthan 95% assay were corrected for assay.

40 grams of duPont's Sclair® high density polyethylene resin was addedto a C. W. Brabender Plastigraph with type-5 mixing blades. The mixerwas heated to 140° C. (just high enough to melt mix the resin) and themixing speed was set at 30 RPM. The polyethylene was melted and then1.69 PHR (corrected for assay) of the peroxide was slowly added to themolten resin. The total mixing time was 6-7 minutes. The compoundedresin was removed and pressed out into a flat sheet between two piecesof Mylar using a room temperature Carver laboratory press (Model C).Upon cooling to room temperature, round discs approximately 1 inch indiameter were cut out of the sheet for crosslinking evaluation of theperoxide in the formulation using the Monsanto ODR-100 Oscillating DiskRheometer (Model R-100).

The Monsanto Rheometer test procedure (ASTM-D-2084-71T) is performed onuncured samples, enclosed under positive pressure in a heated die cavitycontaining a biconical disk. The disk is oscillated (100 cycles/min)through an arc of 3°. The twisting torque, which is measured by adynameter, is the opposition of the molten polymer against the rotationof the disk. The torque required to oscillate the disk is recorded as afunction of time and is proportional to the degree of crosslinking ofthe polymer. The shear modulus increases as percent crosslinkingincreases and the curve generated is a representation of the extent ofcure reaction with time. The test variables recorded from the rheometerare:

M_(H) is the maximum torque generated in the test. It is measured ininch-lbs (or dyne-cms.) and is a measure of the crosslinking attained.

M_(L) is the minimum torque recorded in the test and is measured ininch-lbs (or dyne-cms.). It is a measure of the viscosity of thecompound and is an indicator of scorch. Increased M_(L) values areindicative of scorch.

M_(H) -M_(L) is the difference between maximum and minimum torque valuesrecorded in the test and is an indication of the extent of crosslinking.The greater the M_(H) -M_(L) value, the greater the degree ofcrosslinking.

T_(c) is the cure time in minutes.

T_(c90) is the time required to reach 90% of the maximum torque. It isdefined as (M_(H) -M_(L))0.9+M_(L).

T_(S) is the scorch time in minutes. Scorch is the premature andunwanted vulcanization which occurs during extrusion of a curablepolymeric mixture from the die of an extruder. Scorch time is the timebefore this premature vulcanization occurs. It is the time the sample isat the test temperature before a prescribed increase in viscosityoccurs.

T_(S2) is the time required for the torque to increase two inch-lbsabove M_(L).

T_(S10) is the time required for the torque to increase 10 inch-lbsabove M_(L).

Ten grams of the polyethylene discs prepared above were added to theMonsanto rheometer at a temperature of 385° F. (196° C.) and a mixingspeed of 30 RPM. The torque in inch-lbs was measured vs time. Theresults are summarized in Table III. After correcting for assay, thecrosslinking efficiency of the blends prepared from Examples VII andVIII were slightly lower than the crosslinking efficiency of the blendprepared from pure 1,3-bis(2-t-butylperoxy-2-propyl)benzene (ComparativeExample 1). The M_(H) values and the M_(H) -M_(L) values were slightlylower, the cure times were a little faster and the scorch times (T_(S2))were comparable. The crosslinking results obtained with the blends ofExamples VII and VIII were considerably better than the results obtainedwith the blend prepared with 1,3-bis(2-t-amylperoxy-2-propyl)benzene(Comparative Example 2).

Effectiveness of crosslinking was also determined by extracting 0.5 gramsamples of the crosslinked polyethylene with 100 mls of xylene at 110°C. for 24 hours. The swollen test specimen was removed and surfacexylene removed by air blowing. The test specimen was weighed, placed ina vacuum oven at 100° C. and dried to constant weight under vacuum. Thepercent insolubles and the swell ratio were then determined by thefollowing formulae: ##EQU1##

The % insolubles and swell ratios are found in Table III.

The greater the degree of crosslinking, the lower the amount ofextracted material and the smaller the swell ratio. A large swell ratioindicates a low density of crosslinks and a low swell ratio indicates amore tightly bound structure.

The % insolubles obtained from xylene extraction of the crosslinkedblends prepared from Examples VII and VIII were slightly higher than the% insolubles obtained from the xylene extraction of the crosslinkedblend prepared from pure 1,3-bis(2-t-butylperoxy-2-propyl)benzene(Comparative Example 1) (see Table III) indicating the crosslinkingefficiency of the peroxide mixtures of Examples VII and VIII wereapproximately equivalent to the crosslinking efficiency of the peroxideof Comparative Example 1. In contrast, the % insolubles obtained fromxylene extraction of the crosslinked blend prepared from1,3-bis(2-t-amylperoxy-2-propyl)benzene (Comparative Example 2) wereconsiderably lower indicating the liquid peroxide of Comparative Example2 has a much lower crosslinking efficiency than the peroxides ofExamples VII and VIII. The swell ratios also indicate that the liquidperoxides of Examples VII and VIII are much better crosslinking agentsthan the liquid peroxide of Comparative Example 2 and nearly asefficient as the solid peroxide of Comparative Example 1.

EXAMPLE XXXV

Curing of Ethylene/Propylene Elastomer Copolymer

100 parts by weight of Dutral® CO 054 was mixed with 0.3 parts by weightof sulfur, 5 parts by weight of zinc oxide and 50 parts by weight carbonblack. To this mixture was added approximately 2.2 parts peroxide (seeTable IV) and the resulting mixture homogenized on a calendar for 5minutes. A sample was placed in the oscillating disk rheometer (ODR) at170° C. and the ODR curve generated using an oscillation angle of 3° anda frequency of oscillation of 100 cycles/minute. From the ODR curve, theM_(H), the T_(S10) and the T_(C90) were determined.

The "scorch" times t₂ and t₅ were determined with a Mooney viscometerwith an oscillating disk at 135° C. (standard ASTM D 1646-81). t₂ and t₅are defined as the time required to reach an increase in the viscosityof 2 or 5 Mooney units from the minimal value, respectively. The resultsare summarized in Table IV. The M_(H) values indicate that the peroxideblends of Examples I and III are better curing agents forethylene/propylene elastomers than the peroxides of Comparative Example5.

EXAMPLE XXXVI

Crosslinking of Low Density Polyethylene

100 parts by weight Riblene® CF 2203 low density polyethylene were mixedwith 0.5 part by weight Anox® HB and 0.5 part by weight triallylcyanurate (TAC). To this mixture was added approximately 2.2 parts byweight of peroxide (see Table V) and the resulting mixture blended tohomogeneity on a calendar. A sample was placed in the oscillating diskrheometer at 170° C. and the ODR curve generated using an oscillationangle of 1° and a frequency of oscillation of 100 cycles/minute. Fromthe ODR curve, the M_(H), the T_(S10) and the T_(C90) were determined.The "scorch" times, t₅ and t₁₀ were determined with the Mooneyviscometer at 135° C. The results are summarized in Table V. The largerM_(H) values indicate the peroxides of Examples V and VI are bettercrosslinking agents for low density polyethylene than the peroxides ofComparative Example 5.

                                      TABLE I                                     __________________________________________________________________________    LIQUID PEROXIDE COMPOSITIONS                                                                     I  I  II II III                                                                              III                                                                             IV  Liquid                                                                             Liquid                           EXAMPLE                                                                              m/p TBHP/TAHP                                                                             (m)                                                                              (p)                                                                              (m)                                                                              (p)                                                                              (m)                                                                              (p)                                                                             (m, p)                                                                            at 15 C.                                                                           at 3 C.                          __________________________________________________________________________    X      100:0                                                                             1.25:1  38.9                                                                              0.0                                                                             46.5                                                                              0.0                                                                             11.2                                                                             0.0                                                                             0.0 +    +                                XI     100:0                                                                              1.5:1  44.2                                                                              0.0                                                                             43.5                                                                              0.0                                                                             9.2                                                                              0.0                                                                             0.0 +    +                                XII    100:0                                                                             1.75:1  52.7                                                                              0.0                                                                             38.3                                                                              0.0                                                                             6.3                                                                              0.0                                                                             0.0 +    +                                XIII   100:0                                                                             2.25:1  55.8                                                                              0.0                                                                             35.7                                                                              0.0                                                                             5.2                                                                              0.0                                                                             1.0 +    +                                XIV    100:0                                                                             2.35:1  58.7                                                                              0.0                                                                             35.7                                                                              0.0                                                                             4.5                                                                              0.0                                                                             1.1 +    +                                XV     50:50                                                                             1.00:1  15.3                                                                             13.9                                                                             26.8                                                                             26.6                                                                             9.7                                                                              7.8                                                                             0.0 +    -                                XVI    60:40                                                                             1.35:1  17.9                                                                              8.8                                                                             38.0                                                                             13.9                                                                             9.2                                                                              4.3                                                                             3.9 +    -                                XVII   60:40                                                                             1.00:1  18.6                                                                             10.3                                                                             31.5                                                                             22.2                                                                             11.0                                                                             6.5                                                                             0.0 +    -                                XVIII  65:35                                                                             1.50:1  27.1                                                                             12.5                                                                             31.4                                                                             17.2                                                                             7.3                                                                              3.6                                                                             0.9 -    -                                XIX    65:35                                                                             1.60:1  27.9                                                                             20.1                                                                             24.2                                                                             16.7                                                                             6.9                                                                              3.3                                                                             0.9 +    -                                XX     65:35                                                                             1.75:1  28.1                                                                             16.8                                                                             28.1                                                                             13.3                                                                             9.9                                                                              3.1                                                                             0.7 +    -                                XXI    65:35                                                                             1.85:1  30.6                                                                             17.6                                                                             26.5                                                                             15.9                                                                             5.8                                                                              2.8                                                                             0.8 -    -                                XXII   70:30                                                                             1.50:1  30.0                                                                             12.6                                                                             33.0                                                                             14.2                                                                             8.0                                                                              2.3                                                                             0.0 +    -                                XXIII  70:30                                                                             2.00:1  35.2                                                                             16.7                                                                             25.5                                                                              6.0                                                                             1.9                                                                              0.0                                                                             14.7                                                                              +    -                                XXIV   70:30                                                                             2.25:1  32.4                                                                             17.0                                                                             19.8                                                                             11.8                                                                             1.1                                                                              0.0                                                                             14.4                                                                              +    -                                XXV    75:25                                                                             2.00:1  38.4                                                                             12.6                                                                             30.8                                                                             10.6                                                                             5.5                                                                              1.2                                                                             0.9 -    -                                XXVI   80:20                                                                             1.75:1  38.6                                                                              8.9                                                                             35.1                                                                              9.0                                                                             7.4                                                                              1.0                                                                             0.0 +    +                                XXVII  80:20                                                                             2.00:1  41.0                                                                              9.7                                                                             33.1                                                                              8.6                                                                             5.8                                                                              0.8                                                                             0.9 +    +                                XXVIII 80:20                                                                             2.25:1  43.9                                                                             13.9                                                                             27.7                                                                              8.0                                                                             4.8                                                                              0.7                                                                             1.0 -    -                                XXIX   90:10                                                                             2.00:1  46.6                                                                              5.2                                                                             36.2                                                                              4.4                                                                             6.6                                                                              0.0                                                                             1.0 +    +                                XXX    90:10                                                                             2.35:1  49.7                                                                              0.0                                                                             40.4                                                                              3.0                                                                             6.1                                                                              0.0                                                                             0.8 +    +                                __________________________________________________________________________

                                      TABLE II                                    __________________________________________________________________________    PEROXIDE COMPOSITIONS                                                                           I   I  II  II III III                                       EXAMPLE                                                                              m/p                                                                              TBHP/TAHP                                                                             (m) (p)                                                                              (m) (p)                                                                              (m) (p)                                       __________________________________________________________________________    XXXI   70:30                                                                            1.75:1  33.0                                                                              13.7                                                                             31.1                                                                              13.6                                                                              6.6                                                                              2.0                                       XXXIa             30.4                                                                              11.6                                                                             28.3                                                                              11.9                                                                             16.2                                                                              1.6                                       XXXII  80:20                                                                            2.35:1  44.9                                                                              11.3                                                                             30.8                                                                               8.1                                                                              4.9                                                                              0.0                                       XXXIIa            41.1                                                                               9.9                                                                             28.6                                                                               7.1                                                                             13.3                                                                              0.0                                       XXXIII 60:40                                                                            1.35:1  24.4                                                                              15.0                                                                             29.4                                                                              19.1                                                                              7.6                                                                              4.5                                       XXXIIIa           20.8                                                                              13.0                                                                             26.6                                                                              18.1                                                                             17.4                                                                              4.1                                       __________________________________________________________________________

                                      TABLE III                                   __________________________________________________________________________    CROSSLINKING EVALUATIONS                                                               STARTING RATIO                %       SWELL                          EXAMPLE  t-BuOOH:t-AmOOH                                                                          M(H)                                                                              M(H)-M(L)                                                                            T(C90)                                                                            T(S2)                                                                             INSOLUBLES                                                                            RATIO                          __________________________________________________________________________    Example VII                                                                            2:1        65  64     3.6 1.2 93.5    6.3                            Example VIII                                                                           1:1        70  67     3.6 1.2 93.8    6.4                            Comparative Ex 1                                                                       1:0        73  72     3.8 1.2 93.2    6.1                            Comparative Ex 2                                                                       0:1        61  58     3.4 1.1 90.5    7.2                            __________________________________________________________________________

                                      TABLE IV                                    __________________________________________________________________________    CURING OF ETHYLENE/PROPYLENE ELASTOMER                                        Curing Agent                                                                           PHR  Cure Temp                                                                           M(H) T(S10)                                                                             T(C90)                                                                             t(2) t(5)                                  Peroxide Ex #                                                                          Peroxide                                                                           °C.                                                                          inch-lbs                                                                           seconds                                                                            seconds                                                                            seconds                                                                            seconds                               __________________________________________________________________________    Example 1                                                                              2.12 170   88.5 132  810  582  852                                   Example III                                                                            2.20 170   82.0 138  732  570  852                                   Comparative Ex 5                                                                       2.26 170   74.5 150  672  588  930                                   __________________________________________________________________________

                                      TABLE V                                     __________________________________________________________________________    CROSSLINKING OF LOW DENSITY POLYETHYLENE                                      Curing Agent                                                                           PHR  Crosslinking                                                                         M(H) T(S10)                                                                             T(C90)                                                                             t(5) t(10)                                Peroxide Ex #                                                                          Peroxide                                                                           Temp °C.                                                                      inch-lbs                                                                           seconds                                                                            seconds                                                                            seconds                                                                            seconds                              __________________________________________________________________________    Example V                                                                              2.11 170    19.07                                                                              126  963  1437 1740                                 Example VI                                                                             2.19 170    17.54                                                                              140  1097 1437 1751                                 Comparative Ex 5                                                                       2.26 170    16.93                                                                              135  950  1034 1236                                 __________________________________________________________________________

The subject matter which applicants regard as their invention isparticularly pointed out and distinctly claimed as follows:
 1. Animproved process for the peroxide induce crosslinking of peroxidecrosslinkable polymers and copolymers selected from the group consistingof thermoplastic polymers and elastomeric polymers wherein theimprovement comprises heating 100 parts by weight of said peroxidecrosslinkable polymer or copolymer to a temperature of about 149° C. toabout 260° C. for about 0.5 to about 30 minutes with 0.1 to 10 parts byweight of a liquid peroxide composition comprising a mixture ofcompounds having the structures: ##STR14## and from 0% to about 15% byweight of a compound having the formula IV: ##STR15## wherein R may bet-butyl or t-amyl; R' may be hydrogen, isopropyl, isopropenyl or2-hydroxy-2-propyl; wherein the compound of formula IV is present as themeta isomer, as the para isomer or as a mixture of the meta and paraisomers; wherein the compounds of formulas I, II and III areindependently present as meta isomers, or mixtures of meta and paraisomers, and the relative proportions of the compounds of formulas I,II, III and IV and of the meta and para isomers of the compounds offormulas I, II and III are selected to provide a mixture liquid at 25°C. or lower.
 2. A process as defined in claim 1 wherein the peroxidecrosslinkable polymer is the thermoplastic polymer, polyethylene.
 3. Theprocess of claim 1 where 0.5-5 parts of the liquid peroxide blend ofclaim 1 is heated to 350°-400° F. with 100 parts polyethylene for 2 to15 minutes.